Prevent 2 unnecessary QString allocations for QString::number(0u)

QLocaleData::unsLongLongToString uses qulltoa, which will allocate a
zero-length QArrayData. Then with padding a single 0 was put in a
QString, which gets prepended to the result. By taking care of this
special case, we can now also fast-path the common case where base=10
and no flags nor precision was provided.

Change-Id: Ia893b0ea4c77634c24e7cef5aafb06d0ef44c507
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/src/corelib/tools/qlocale.cpp b/src/corelib/tools/qlocale.cpp
index 5eb45f3b2c..dcdf6b5ed7 100644
--- a/src/corelib/tools/qlocale.cpp
+++ b/src/corelib/tools/qlocale.cpp
@@ -3005,14 +3005,18 @@ QString QLocaleData::unsLongLongToString(const QChar zero, const QChar group,
                                             int base, int width,
                                             unsigned flags)
 {
+    const QChar resultZero = base == 10 ? zero : QChar(QLatin1Char('0'));
+    QString num_str = l ? qulltoa(l, base, zero) : QString(resultZero);
+
     bool precision_not_specified = false;
     if (precision == -1) {
+        if (flags == NoFlags)
+            return num_str; // fast-path: nothing below applies, so we're done.
+
         precision_not_specified = true;
         precision = 1;
     }
 
-    QString num_str = qulltoa(l, base, zero);
-
     uint cnt_thousand_sep = 0;
     if (flags & ThousandsGroup && base == 10) {
         for (int i = num_str.length() - 3; i > 0; i -=3) {
@@ -3021,7 +3025,6 @@ QString QLocaleData::unsLongLongToString(const QChar zero, const QChar group,
         }
     }
 
-    const QChar resultZero = base == 10 ? zero : QChar(QLatin1Char('0'));
     const int zeroPadding = precision - num_str.length()/* + cnt_thousand_sep*/;
     if (zeroPadding > 0)
         num_str.prepend(QString(zeroPadding, resultZero));